Color television tube screen having strip interruptions for reducing perceptibleness of stripe structure



3 April 19, 1966 COLOR TELEVISION TUBE SCREEN HAVING STRIP INTERRUPTIONS FOR REDUCING PERCEPTIBLENESS OF swam: STRUCTURE E. J. VAN BARNEV-ELD ETAL 9 IO 4 i7 Filed March 2, 1962 FIG.4

INVENTOR5 EVERT J.VAN BARNEVELD EDWARD F DE HAAN United States Patent C) 3,247 412 CGLOR TELEVISION TUBE SCREEN HAVING STRIP INTERRUPTIONS FOR REDUCING PERCEPTIBLENESS F STRIPE STRUCTURE Evert Jan van Barneveld and Edward Folrlro de Haan,

both of Emmasingel, Eindhoven, Netherlands, assignors to North American Phiiips Company, Inc., New York, N.Y., a corporation of Delaware Filed Mar. 2, 1962, Ser. No. 176,977 Claims priority, application Netherlands, Mar. 8, 1961, 262,149 Ciaims. (Ci. 313-92) The invention relates to cathode-ray tubes for displaying colored images, for particularly color television images.

In most tubes for displaying color television images there is provided on the inner side of a window part of the tube envelope a display screen built up from several, usually three, luminescent substances which on excitation by electrons emit light of different colors, usually red, green and blue. These substances are not mixed on the screen at random but are always arranged according to a recurrent pattern in discrete surfaces, the shape of which is substantially determined by the nature of the color selecting means. This arrangement will be referred to hereinafter as the macrostructure.

Two large groups of macrostructures can be distinguished, that is to say, a group in which the luminescent substances are arranged in dots and a group in which they are arranged in parallel stripes.

Screens having a macro-stripe-structure are used, for example, in tubes in which color selection is effected with the aid of two interdigital grids spaced at a small distance from and in front of, that is to say at the gunside of, the display screen. The macro-stripes-structure is also found in tubes of the type in which the screen comprises so-called index stripes, that is to say, stripes with the aid of which a control signal can be produced by which small deviations of the beam position may be corrected. I

The most important representative of the tubes having a macro-stripe-structure has a so-called shadow mask arranged at a small distance in front of the display screen. This mask is provided wit-h a large number of small holes the positioning of which is correlated with the positioning of the dots on the screen. When three differently luminescing substances are used, in this tube the dots on the screen are arranged in the vertices of regular triangles so that a dot luminescing in a different color is arranged in each vertex.

In tubes having a macro-stripe-structure the line scanning system may be at an arbitrary angle to the direction of the stripes. In practice, however, the line scanning system extends either parallel to the stripes or at right angles thereto. It will be appreciated that in the case of scanning parallel to the stripes the eye perceives the stripe structure of the image. However, it has been found that the eye also perceives the stripe structure when the line scanning system is at right angles to the direction of the color stripes.

\ In a screen having macro-dot-structure this phenomenon provides substantially no difficulty, although in this case also dots luminescing in the same color and aligned with one another might be correlated to a line by the eye. This may be explained by the presence of the intervals between dots which may be correlated to form a line.

As a large number, of observations have shown, an image on a screen having a macro-dot-structure is substantially structureless to the eye, and this is more agreeable than :an image in which a line structure is perceived.

A cathode-ray tube in accordance with the invention for displaying colored images has a display screen comprising at least two substances which on excitation by electrons luminesce in different colors and are arranged according to a recurrent pattern of parallel stripes so that two adjacent stripes luminesce in dilferent colors, and it is characterized in that at least the luminescent stripes of the substance giving the impression of greatest brightness to the eye have non-luminescing interruptions so that the number of interruptions in a stripe is at least equal to one tenth of the total number of stripes on the screen, the spacing between two successive interruptions in a stripe is at least equal to thrice the width of the stripe and the length of an interruption is at most equal to twice the width of the stripe.

Although in a cathode-ray tube in accordance with the invention there is a distinct macro-stripe-Structure, the impression made on the eye by an image traced on such a screen is substantially structureless, at least no clear stripe structure is perceived.

Since tests have shown that the stripe structure perceived by the eye is substantially produced by the stripes on the screen making the strongest light impression on the eye, these stripes must in any case include the abovedescribed interruptions. By providing all stripes with interruptions, the perception of the stripe structure is further reduced.

Since, when luminescent substances emitting blue, red or green light are used, the green color produces the strongest brightness impression on the eye, in this embodiment the interruptions will in any case be provided in the stripes emitting green light.

Since the human eye is highly'sensitive to symmetry and regularity, the interruptions are preferably arranged regularly. For the same reason the interruptions are preferably staggered in two adjacent color stripes in a special embodiment of the invention. Thus, no two interruptions are adjacent in a direction at rig-ht angles to the direction of length of the color stripes.

The same object is achieved in another embodiment of a tube in accordance with the invention, in which the interruptions in all the stripes of a set of successive stripes containing all the differently luminescent substances, in a direction at right angles to the direction of length of the stripes are disposed side by side, the interruptions being staggered in the successive sets of stripes. In order that the invention may readily be carried into effect, two embodiments thereof will now be described, by Way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a diagrammatic longitudinal section through a tube in accordance with the invention,

FIGURE 2 shows to an enlarged scale the structure of a display screen suitable for a tube of the kind shownin FIGURE 1, and

FIGURE 3 shows another embodiment of a display screen suitable for use in a tube of the kind shown in FIGURE 1.

FIGURE 4 shows still another embodiment of a display screen similar to that shown in FIGURE 2.

In FIGURE 1, a display screen 2 having macro-stripestructure is provided on the inside of a window 1 of the cathode-ray tube. The tube contains an electron gun 3 producing an electron beam which with the aid of a deflector system 4'scans the display screen 2 according to a particular raster. A set of interdigital grids 5 is capable of providing color selection.

In FIGURE 2, colored stripes are designated 6, 7, 8, 9, l0 and 11. The stripes 6 and 9 when luminescing emit red light, the stripes 7 and 10 emit green light and the stripes 8 and 11 emit blue light. Each stripe has nonluminescing interruptions 12. The spacing a between two interruptions is at least equal to thrice the width b of the emit light to which the eye is most sensitive having a stripe. The length of each interruption is at most equal to 2b. The dimensions a, b and 0 need not necessarily be the same throughout the entire screen but in any case the conditions must be satisfied that in an interrupted stripe the number of interruptions should be at least equal to one tenth of the total number of color stripes on the screen.

The interruptions need not invariably have the rectangular shape shown in the figures. The ends of the luminescent areas may be rounded.

FIGURE 3 shows part of the display screen of another embodiment of .a tube in accordance with the invention. This screen has luminescent stripes 13, 14, 15, 16, 17 and 18. When luminescing, the stripes 13 and 16 emit red light, the stripes 14 and 17 green light and the stripes 15 and 18 blue light. As will be seen from the figure, in this embodiment the interruptions 19 in a set of color stripes, that is to say in a number of adjacent stripes including all colors that is to say the stripes 13, 14, 15 and 16, 17, 18, are arranged side by side, but they are staggered in the various sets.

For further illustration of the invention, the following details are given of a display screen providing highly satisfactory images without inconvenient perceivable stripe structure.

In a rectangular area of 400 x 500 mm., 430 sets of stripes were arranged parallel to the shorter sides of the rectangle. Each set of stripes comprised 3 parallel stripes of luminescent material emitting red, green and blue light respectively. The width of each stripe of luminescent material was 0.22 mm. and its length was 400 mm. These stripes were separated by non-lurninescent stripes having a width of 0.22 mm.; the. latter stripes served in known manner to reduce the color contamination. Each luminescent stripe included 307 interruptions of length 0.30 mm. which were evenly distributed along the stripe, and 308 luminescent areas of length 1.0 mm.

FIGURE 4 shows still another embodiment of the invention in which the stripe structure is similar to that shown in FIG. 2 except that only the green stripes 7 have nonluminescing portions 12 which interrupt these stripes.

What is claimed is:

1. A color television tube comprising an image screen, said image screen comprising a supporting member of transparent material having a plurality of parallel phosphor stripes each of given width which on electron excitation emit light of different colors, said stripes being in a recurrent pattern so that adjacent stripes when luminescing emit light of different colors, at least those stripes which emit light to which the eye is most sensitive having a plu rality of non-luminescent portions each of given length and spaced apart a given distance which interrupt the stripe at successive intervals, the number of non-luminescent portions in one of said stripes being not less than one-tenth the total number of stripes, the spacing between two successive interruptions in a stripe being not less than three times the width of the stripe and the length of the non-luminescing port-ion not exceeding twice the width of the stripe, and means for scanning the image screen with an electron beam.

2. A color television tube comprising an image screen, said image screen comprising a supporting member of transparent material having a plurality of parallel phosphor stripes each of given width which on electron excitation emit light of different colors, said stripes being in a recurrent pattern so that adjacent stripes when luminescing emit light of different colors, at least those stripes whilch P rality of uniformly distributed non-luminescent portions each of given length and spaced apart a given distance which interrupt the stripe at successive intervals, the number of non-luminescent portions in one of said stripes being not less than one-tenth the total number of stripes, the spacing between two successive interruptions in a stripe being not less than ,three times the width of the stripe and the length of the n-on-luminescing portion not exceeding twice the width of the stripe, and means for scanning the image screen with an electron beam.

3. A color television tube comprising an image screen, said image screen comprising a supporting member of transparent material having a plurality of parallel phosphor stripes each of given width which on electron excitation emit light of different colors, said stripes being in a recurrent pattern so that adjacent stripes when luminescing emit light of different colors, at least those stripes which emit light to which the eye is most sensitive havingnonluminescent portions each of given length spaced apart a given distance which interrupt the stripe at successive intervals, said non-luminescent portions being staggered in successive stripes so that in a direction at right angles to the direction of length of the stripes, no two non-luminescent portions are located side-by-side, the number of non-luminescent portions in one of said stripes being not less than one-tenth the total number of stripes, the spacing between two successive interruptions in a stripe being not less than three times the width of the stripe and the length of the non-luminescing portion not exceeding twice the width of the stripe, and means for scanning the image screen with an electron beam.

4. A color television tube comprising an image screen, said image screen comprising a supporting member of transparent material having a plurality of parallel phosphor stripes each of given width which on electron excitation emit light of difierent colors, said stripes being in sets constituting a recurrent pattern so that adjacent stripes when luminescing emit light of different colors, at least those stripes which emit light to which the eye is most sensitive having non-luminescent portions each of given length spaced apart a given distance which interrupt the stripe at successive intervals, said non-luminescent portions in the stripes being disposed side-by-side in a direction at right angles to the direction of length of the stripes, the non-luminescent portions in successive sets being staggered in position, the number of non-luminescent portions in one of said stripes being not less than one-tenth the total number of stripes, the spacing between two successive interruptions in a stripe being not less than three times the width of the stripe and the length of the nonluminescing portion not exceeding twice the width of the stripe, and means for scanning the image screen with an electron beam.

5. A color television tube comprising an image screen, said image screen comprising a supporting member of transparent material having a plurality of parallel phosphor stripes each of given width which on electron excitation emit light of dilferent colors, said stripes being in sets constituting a recurrent pattern so that adjacent stripes when luminescing emit light of different colors, one of said stripes in each of said sets emitting light to which the eye is most sensitive, said latter stripe having a plurality of non-luminescent portions each of given length spaced apart a given distance which interrupt the stripe at successive intervals, the number of non-luminescent portions in one of said stripes not exceeding one-tenth the total number of stripes, the spacing between two successive interruptions in a stripe being not less than three times the width of the stripe and the length of the non-luminescing portion not exceeding twice the width of the stripe, and means for scanning the image screen with an electron beam.

Reierences Cited by the Examiner UNITED STATES PATENTS 2,863,079 12/ 1958 Oestreicher. 2,888,603 5/ 1959 Laiierty. 2,922,073 l/ 1960 Oestreicher.

GEORGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, Examiner. 

1. A COLOR TELEVISION TUBE COMPRISING AN IMAGE SCREEN, SAID IMAGE SCREEN COMPRISING A SUPPORTING MEMBER OF TRANSPARENT MATERIAL HAVING A PLURALITY OF PARALLEL PHOSPHOR STRIPES EACH OF GIVEN WIDTH WHICH ON ELECTRON EXCITATION EMIT LIGHT OF DIFFERENT COLORS, SAID STRIPES BEING IN A RECURRENT PATTERN SO THAT ADJACENT STRIPS WHEN LUMINESCING EMIT LIGHT OF DIFFERENT COLORS, AT LEAST THOSE STRIPES WHICH EMIT LIGHT TO WHICH THE EYE IS MOST SENSITIVE HAVING A PLURALITY OF NON-LUMINESCENT PORTIONS EACH OF GIVEN LENGTH AND SPACED APART A GIVEN DISTANCE WHICH INTERRUPT THE STRIPE AT SUCCESSIVE INTERVALS, THE NUMBER OF NON-LUMI- 